Implantable medical devices may be used to monitor a patient condition and/or deliver therapy to the patient. In long term or chronic uses, implantable medical devices may include a rechargeable power source (e.g., comprising one or more capacitors or batteries) that extends the operational life of the medical device to weeks, months, or even years over a non-rechargeable device.
When the energy stored in the rechargeable power source has been depleted, the patient may use an external charging device to recharge the power source. Since the rechargeable power source is implanted in the patient and the charging device is external of the patient, this charging process may be referred to as transcutaneous charging. In some examples, transcutaneous charging may be performed via inductive coupling between a primary coil in the charging device and a secondary coil in the implantable medical device. When a current is applied to the primary coil and the primary coil is aligned to the secondary coil, electrical current is induced in the secondary coil within the patient. Therefore, the external charging device does not need to physically connect with the rechargeable power source for charging to occur.